CN113722926A - Square lithium battery electric-thermal coupling modeling error source analysis method - Google Patents
Square lithium battery electric-thermal coupling modeling error source analysis method Download PDFInfo
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Abstract
The invention relates to an electric-thermal coupling modeling error source analysis method for a square lithium battery, and belongs to the technical field of batteries. According to the method, a universal error analysis framework is constructed to systematically analyze error sources possibly introduced in the control-oriented electric-thermal coupling modeling process of the large-size square battery. First, a computationally efficient electrical-thermal coupling model needs to be established for large-sized prismatic cells. Then, taking the modeling thought as an example, error sources possibly introduced in three stages of data acquisition, heat generation calculation and heat transfer simulation are comprehensively considered, specifically including error sources in the aspects of data acquisition and preprocessing, a heat generation calculation method, heat/electric heat submodel parameterization, thermal interaction analysis between a battery body and positive and negative electrode lugs and the like, so that a group of optimal simulation combinations are obtained through the error analysis framework, the electric heat simulation precision of the large power battery facing to control is improved, and an accurate model basis is provided for online electric heat monitoring and control optimization of a battery system.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to an electric-thermal coupling modeling error source analysis method for a square lithium battery.
Background
Accurate and computationally efficient electrical-thermal coupling simulations are critical to thermal safety and performance management of electric vehicles and smart grid energy storage systems. The thermal process of a battery typically includes heat generation, heat dissipation, and heat accumulation, and many models of electrical-thermal coupling of battery systems have been reported. The electrothermal coupling models may be divided into control-oriented models and design-oriented models according to application scenarios. Among them, the control-oriented model has been widely used in online systems because it can make good trade-off between prediction accuracy, computational complexity, and parameterization difficulty. But inevitably introduces modeling errors from three aspects of data acquisition, heat generation calculation and heat transfer simulation during model assumptions and simplification.
The electro-thermal coupling simulation of a battery typically requires the acquisition of experimental data including current, voltage and temperature. It is well known that temperature measurement sequences have a large measurement noise compared to current and voltage data. It is necessary to evaluate the influence of different degrees of measurement noise on the prediction accuracy of the control-oriented electrical-thermal coupling model.
The heat source term of the control-oriented electrothermal coupling model is usually calculated by a typical Bernardi heat generation formula. Research shows that if the thermal effect of the battery caused by the phase change of the active material and the concentration gradient of lithium ions in the electrochemical reaction is not considered, the simulation method can achieve satisfactory precision. This simplified thermogenesis model contains both irreversible and reversible heat portions. The calculation method of the irreversible heat includes two methods: an overpotential-based method and an equivalent internal resistance-based method. The equivalent internal resistance of the battery can be obtained through several typical methods, such as direct calculation through ohm's law and parameter identification based on an equivalent circuit model. Obviously, this combines multiple heat production calculation methods. Although these methods are sufficiently computationally efficient, there is currently no relevant comparative study and no suitable heat production calculation method can be provided for a specific electric heat simulation. For the calculation of the reversible heat, the proportion of the reversible heat to the total heat generation is generally small, and the calculation is carried out by interpolation or fitting technology as long as the functional relationship between the entropy heat coefficient and the state of charge SOC is obtained in advance.
Heat transfer of the battery includes heat conduction inside the battery and heat exchange between the battery and the external environment (including thermal convection and thermal radiation). According to the heat generation assumption of the battery, the control-oriented electric heating model can be divided into a centralized heat generation model and a distributed heat generation model. The centralized heat production model, also referred to as a thermal equivalent loop model, is similar to an equivalent circuit model derived based on kirchhoff's law. Although these models can only obtain temperature information of a single location, they are computationally efficient and highly accurate to predict, and are currently widely used for online temperature monitoring of various geometry battery systems. For distributed heat generation models, which are typically represented by energy conservation equations needed to satisfy specific heat transfer boundaries, various order reduction techniques can be used to solve, such as polynomial approximation, quadratic assumptions, integral method approximation, galaogin approximation, finite difference methods, and the like. Compared with a centralized heat production model, the model can obtain higher prediction precision under the condition of increasing a small amount of calculation cost, and can obtain detailed temperature distribution, so that more effective battery thermal management is realized. For the above heat transfer models, although their model assumptions and simplifications vary, they all require parameterization of the model to determine the unknown parameters. However, there are few current studies reporting possible factors that influence the accuracy of model parameterization. For example, how to optimize the arrangement scheme of the temperature sensors to minimize the error of the model parameterization and how to consider the influence of the current multiplying power, the external cooling environment, the working temperature and the loading condition on the model parameters need further research. Especially for square batteries, at least a two-dimensional electrothermal model is needed to accurately capture the thermodynamics of the batteries, which further highlights the important significance of the arrangement optimization of the temperature sensor. In addition, if an accurate electrical-thermal coupling model is to be established, the influence of thermal interaction between the positive and negative electrode tabs and the battery body on the temperature distribution of the large-size battery body needs to be considered carefully.
Based on the above, the invention aims to provide a group of optimal simulation combinations by analyzing various error sources possibly occurring in the control-oriented electric heating coupling simulation process in detail and combining quantitative evaluation and longitudinal and transverse comparison analysis, thereby realizing the optimal compromise of the large-size square battery control-oriented electric heating coupling simulation in multiple aspects of prediction precision, calculation complexity and model applicability. The technical scheme of the invention can solve the problem of the existing research scheme to a great extent and provides reference for more accurate and practical electrothermal coupling simulation.
Disclosure of Invention
In view of this, the present invention provides an analysis method for an electric-thermal coupling modeling error source of a square lithium battery.
In order to achieve the purpose, the invention provides the following technical scheme:
an electric heating coupling modeling error source analysis method for a square lithium battery comprises the following steps:
s1: performing necessary modeling assumption and simplification treatment on the heat production and heat transfer processes of the large-size square battery, and independently modeling the positive electrode lug, the negative electrode lug and the battery body of the battery to establish a control-oriented electric heating coupling model;
s2: selecting a large-size square lithium battery, developing experimental design, carrying out experiments, carrying out necessary pretreatment on battery data, and establishing a characteristic test, a constant-current working condition and a dynamic working condition data set of the battery;
s3: in the overview of the high-efficiency heat production calculation method calculated at the present stage, a widely-applied heat production calculation method is selected as an analysis object, and quantitative analysis and comparative research are carried out on the basis of the established electric-thermal coupling model and the collected experimental data set;
s4: each thermal/electric heating submodel in the parametric electric thermal coupling model quantitatively analyzes error sources possibly introduced into the parametric electric thermal coupling model;
s5: researching the thermal interaction between the battery tab and the battery body, and quantitatively analyzing the influence of the heat conduction between the battery tab and the battery body on the temperature distribution of the battery body;
s6: and comprehensively analyzing error sources possibly introduced in the control-oriented electrothermal coupling modeling process to obtain a group of optimal simulation combinations, and verifying the simulation precision and the universality of the combination by experiments.
Optionally, in step S1, for the positive and negative tabs of the battery, a concentrated mass model is established to describe the thermal behavior of the region in consideration of the material characteristics and the smaller geometric size of the tabs; aiming at a battery body, establishing a two-dimensional low-order electric heating model to describe the thermal behavior of the region; and establishing an empirical heat transfer model for describing the thermal interaction between the battery body and the anode and cathode lugs.
Optionally, in step S2, the designed and implemented experiment includes a characteristic test, a constant current discharge test and a dynamic condition test of the battery, where the characteristic test includes a static capacity test and a mixed pulse power characteristic test HPPC of the battery at different temperatures, the constant current discharge test includes a constant current discharge test at different magnifications, and the dynamic condition test includes a federal city driving condition FUDS and a new standard european cycle test condition NEDC at different temperatures. In addition, the preprocessing of the battery data mainly comprises the steps of removing abnormal data, supplementing missing data and reducing noise of the data, and the established experimental data set comprises current, voltage and temperature data of each measuring point.
Optionally, in step S3, there are three heat generation calculation methods widely used at present: the method based on the equivalent internal resistance can be divided into a voltage difference method and a parameter identification method based on an equivalent circuit model according to the acquisition mode of the equivalent internal resistance.
Optionally, in step S4, the parameterization of each thermal/electrical thermal submodel in the electrical-thermal coupling model refers to the parameterization of the concentrated mass thermal model of the positive and negative electrode tabs and the parameterization of the two-dimensional low-order electrical-thermal coupling model of the battery body. In the parameterization process of the concentrated mass thermal model, the influence of the working temperature of the battery, the external cooling condition, the current multiplying power and the loading working condition on the model parameters is considered; in the parameterization process of the two-dimensional low-order electrical-thermal coupling model, the influence of the temperature measuring point combination on the parameterization precision of the model is mainly considered.
Optionally, in the step S5, the influence of the thermal conduction between the battery tab and the battery body on the temperature distribution of the battery body is quantitatively analyzed by evaluating the prediction accuracy of the electrical-thermal coupling model in consideration of and without consideration of the thermal interaction between the battery tab and the battery body.
Optionally, in step S6, the relative root mean square error RRMSE is used as an evaluation index, the prediction accuracy of the maximum temperature and the maximum temperature difference of the battery is mainly considered, all possible error sources in the control-oriented electrothermal coupling simulation process are comprehensively analyzed, a group of optimal simulation combinations is obtained, and then the prediction accuracy and the universality of the optimal simulation combinations are verified in different working condition scenarios.
Optionally, for the concentrated mass thermal models of the positive and negative electrode tabs, the heat generation term is only in consideration of ohmic heat generation; for the two-dimensional low-order electric heating model of the battery body, the heat production term is calculated based on a typical Bernardi heat production formula, and the heat production of the battery body is considered to comprise reversible heat and irreversible heat. In addition, for the heat transfer behavior of the battery body, a two-dimensional energy conservation equation is used for description, the model reduction of the two-dimensional partial differential equation is realized by utilizing a Chebyshev-Galerkin approximation method, and the two-dimensional partial differential equation is converted into a plurality of ordinary differential equations for solving. For the heat flow exchange between the positive and negative electrode tabs and the battery body, an empirical heat conduction equation is used for simulation, and the heat flow exchange amount needs to be reasonably distributed to each discrete unit according to the heat flow conduction distance. Because of the model reduction method according to the present invention, the battery body can be discretized into several cells.
Optionally, when the simulation accuracy of the three heat generation calculation methods is compared, it is difficult to directly and accurately measure the heat generation amount of the battery by using an experimental method, so that a reference standard is lacked when the heat generation calculation methods are directly compared. In order to solve the problem, the method avoids direct comparison of heat generation calculation methods, and indirectly evaluates the three heat generation calculation methods by comprehensively considering the heat generation calculation methods and other factors influencing battery electric-thermal coupling modeling and according to the prediction precision of a final model. Although the idea cannot accurately know which heat production calculation method can most accurately describe the real heat production of the battery, the idea can determine which heat production calculation method is most suitable for the current electric-thermal coupling simulation.
The invention has the beneficial effects that:
(1) aiming at the large-size square battery, the method can comprehensively analyze error sources possibly introduced by the control-oriented electric heating coupling model in the data acquisition, heat generation calculation and heat transfer simulation stages in detail, can provide an optimal simulation combination for the battery system through quantitative evaluation and comparative analysis, and realizes the optimal compromise of the control-oriented electric heating coupling simulation of the large-size square battery in multiple aspects of prediction precision, calculation complexity and model applicability;
(2) the invention provides a set of universal error source analysis framework for calculating high-efficiency electro-thermal coupling simulation of a large-size square battery, which can be suitable for soft package batteries and thin square batteries of various electrochemical systems and can also be applied to error source analysis in the control-oriented electro-thermal coupling modeling process of cylindrical batteries;
(3) the heat production quantity of the battery under various test conditions cannot be accurately measured, so that the lack of reference values is easily caused when the direct comparison of the heat production calculation method is carried out, but the direct comparison of the heat production calculation precision is ingeniously avoided, and the three heat production calculation methods are indirectly evaluated by comprehensively considering the heat production calculation method and other factors influencing the battery electric-thermal coupling modeling according to the prediction precision of the final model. This concept enables determination of which heat production calculation method is best suited for current electrical-thermal coupling simulations.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a general flow diagram of the present invention;
FIG. 2 is a schematic view showing the heat dissipation condition and the arrangement of temperature sensors of a large-sized prismatic battery according to the present invention;
FIG. 3 is a schematic diagram of the present invention showing the electro-thermal coupling simulation for a large-sized prismatic battery;
FIG. 4 is a schematic diagram of the distribution rules of heat flux exchange between the positive and negative electrode tabs and the battery body according to the present invention;
FIG. 5 is a flow chart of the Chebyshev-Galerkin approximation method for achieving order reduction of a heat conservation equation model in the present invention;
FIG. 6 is an explanatory diagram of an experimental design of the present invention;
fig. 7 is a framework of analysis of error sources that may occur during a computationally efficient electrical-thermal coupling simulation of a large-sized prismatic cell of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.
Referring to fig. 1, an analysis method for an electric-thermal coupling modeling error source of a square lithium battery includes the following steps:
s1: performing necessary modeling assumption and simplification treatment on the heat production and heat transfer processes of the large-size square battery, and independently modeling the positive electrode lug, the negative electrode lug and the battery body of the battery to establish a control-oriented electric heating coupling model;
s2: selecting a large-size square lithium battery, developing experimental design, carrying out experiments, carrying out necessary pretreatment on battery data, and establishing a characteristic test, a constant-current working condition and a dynamic working condition data set of the battery;
s3: in the overview of the high-efficiency heat production calculation method calculated at the present stage, a widely-applied heat production calculation method is selected as an analysis object, and quantitative analysis and comparative research are carried out on the basis of the established electric-thermal coupling model and the collected experimental data set;
s4: each thermal/electric heating submodel in the parametric electric thermal coupling model quantitatively analyzes error sources possibly introduced into the parametric electric thermal coupling model;
s5: researching the thermal interaction between the battery tab and the battery body, and quantitatively analyzing the influence of the heat conduction between the battery tab and the battery body on the temperature distribution of the battery body;
s6: and comprehensively analyzing error sources possibly introduced in the control-oriented electrothermal coupling modeling process to obtain a group of optimal simulation combinations, and verifying the simulation precision and the universality of the combination by experiments.
Referring to fig. 2, in step S1, assuming that the temperature distribution of the large-sized square lithium battery exists only in the plane of the battery, the periphery of the battery exchanges heat with the external environment, including heat convection and heat radiation. In addition, in order to capture as much as possible the thermal behavior in the plane of the battery, the temperature sensor arrangement takes into account nine temperature measurement points A-I, corresponding to the output T of the proposed electrical-thermal coupling model1-T9Sufficient temperature data can be measured and used for subsequent electrothermal coupling modeling and model precision and effectiveness verification.
Referring to fig. 3, for the positive and negative tabs of the battery, a concentrated mass model is established to describe the thermal behavior of the region in consideration of the material characteristics and the smaller geometric size of the tabs; aiming at the battery body, establishing a two-dimensional low-order electrical thermal coupling model to describe the thermal behavior of the region; and establishing an empirical heat transfer model for describing the thermal interaction between the battery body and the anode and cathode lugs. In particular, the amount of the solvent to be used,
for the concentrated mass thermal model of the positive and negative electrode tabs, the general expression is as follows:
where ρ ist、Cpt、Tt、qt、qct、T∞The density, specific heat capacity, temperature, heat generation rate, heat conducted to the battery body per unit time and ambient temperature of the tab are respectively. Heat flux qctThis can be obtained empirically by the following formula:
qct＝hctAct(Tt-Tm)
wherein h isct、Act、TmRespectively, the thermal contact coefficients describing the influence of the internal contact resistance on the thermal conduction limitThe contact area of the battery tab and the body and the temperature of the discrete unit of the battery body closest to the tab position. As shown in fig. 4, the heat conducted to the battery body needs to be distributed to each discrete cell on the battery plane according to a certain distribution rule according to the basic formula:
wherein q isct,kAnd betactRespectively, the heat flux assigned to the kth discrete unit and the adjustment factor used to determine the actual effect of the heat flux on the temperature change of the discrete unit. Coordinate (x)t,yt) And (x)i,yi) Respectively, the position of the tab in a cartesian coordinate system and the position of the kth discrete unit. From this equation, the heat flow distribution is inversely proportional to the distance of heat transfer.
Heat production term qtOnly considering ohmic heat generation:
qt＝I2Rs,t
wherein equivalent internal resistance R of the tabs,tCan be identified by experimental data.
For the battery body, the temperature distribution obeys a two-dimensional unsteady heat conduction equation under Cartesian coordinates:
ρCpDtT-kxDxxT-kyDyyT＝q
as in fig. 2, the following boundary conditions are satisfied:
at x-0 and x-w,
at y-0 and y-l,
where T is a temperature function related to location and time, and q is a heat generation rate per unit volume of the battery.
Subscripts r, l, t, and b represent the right, left, upper, and lower boundaries of the battery, respectively. k is a radical ofxAnd kyRefers to non-uniform thermal conductivity in the x and y directions, respectively. Considering the battery structure, both are considered to be equal in the present invention. x ═ 0, w]，y＝[0,l]Where w and l are the width and length of the cell, respectively. ρ and CpThe volume average density and the specific heat capacity of the battery are respectively. h isx＝[hr,-hl]And hy＝[ht,-hb]Equivalent heat dissipation coefficients in the x and y directions, respectively. T is∞,x＝[Tr,∞,Tl,∞]And T∞,y＝[Tt,∞,Tb,∞]The ambient temperatures in the two directions of the battery, respectively, can be assumed to be equal in the test environment of the present invention. As shown in table 1, the heat generation term q thereof is calculated based on a typical Bernardi heat generation formula, taking into consideration that the heat generation of the battery body includes reversible heat and irreversible heat. Three heat production calculation methods are considered in the invention, and the heat production calculation method most suitable for the current electric-thermal coupling simulation is selected through transverse comparison analysis. It should be noted that in calculating the heat generation rate q, the distribution of the heat flow between the positive and negative electrode tabs and the battery body in each discrete unit is also considered.
As shown in fig. 5, the model order reduction of the second-order partial differential equation can be realized by using the chebyshev-galaogin approximation method, and the second-order partial differential equation is converted into a plurality of ordinary differential equations for solution. The modeling method can obtain good compromise among model precision, calculation complexity and parameterization difficulty, and has potential application to online temperature monitoring and performance management of a battery management system.
Referring to fig. 6, in step S2, the designed and implemented experiments include a characteristic test, a constant current discharge test and a dynamic condition test of the battery, where the characteristic test includes a static capacity test and a mixed pulse power characteristic test HPPC of the battery at different temperatures, the constant current discharge test includes a constant current discharge test at different rates, and the dynamic condition test includes a federal city driving condition FUDS and a new european cycle test condition NEDC at different temperatures. In addition, the preprocessing of the battery data mainly comprises the steps of removing abnormal data, supplementing missing data and reducing noise of the data, and the established experimental data set comprises current, voltage and temperature data of each measuring point.
Please refer to table 1.
TABLE 1 calculation formula for heat production currently in wide application
In step S3, there are three methods for calculating heat generation that are widely used at present: the method based on the equivalent internal resistance can be divided into a voltage difference method and a parameter identification method based on an equivalent circuit model according to the acquisition mode of the equivalent internal resistance. In addition, when the simulation precision of the three heat production calculation methods is compared, it is difficult to directly and accurately measure the heat production quantity of the battery by using an experimental method, so that a reference standard is lacked when the heat production calculation methods are directly compared. In order to solve the problem, the method avoids direct comparison of heat generation calculation methods, and indirectly evaluates the three heat generation calculation methods by comprehensively considering the heat generation calculation methods and other factors influencing battery electric-thermal coupling modeling and according to the prediction precision of a final model. Although the idea cannot accurately know which heat production calculation method can most accurately describe the real heat production of the battery, the idea can determine which heat production calculation method is most suitable for the current electric-thermal coupling simulation.
Referring to fig. 7, in step S4, the parameterization of each thermal/electrical thermal submodel in the electrical-thermal coupling model refers to the parameterization of the concentrated mass thermal model of the positive and negative electrode tabs and the parameterization of the two-dimensional low-order electrical-thermal coupling model of the battery body. In the parameterization process of the concentrated mass thermal model, the influence of the working temperature of the battery, the external cooling condition, the current multiplying power and the loading working condition on the model parameters is considered; in the parameterization process of the two-dimensional low-order electrical-thermal coupling model, the influence of the temperature measuring point combination on the parameterization precision of the model is mainly considered.
Referring to fig. 7, in step S5, the influence of the thermal conduction between the battery tab and the battery body on the temperature distribution of the battery body is quantitatively analyzed by evaluating the prediction accuracy of the electrical-thermal coupling model in consideration of and without consideration of the thermal interaction between the battery tab and the battery body.
Referring to fig. 7, in step S6, the relative root mean square error RRMSE is used as an evaluation index, the prediction accuracy of the maximum temperature and the maximum temperature difference of the battery is mainly considered, all possible error sources in the control-oriented electrothermal coupling simulation process are comprehensively analyzed, a group of optimal simulation combinations is obtained, and then the prediction accuracy and the universality of the optimal simulation combinations are verified in different working condition scenarios.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (9)
1. An electric heating coupling modeling error source analysis method for a square lithium battery is characterized by comprising the following steps: the method comprises the following steps:
s1: modeling assumption and simplification are carried out on the heat production and heat transfer processes of the large-size square battery, and an electric heating coupling model facing control is established by independently modeling a positive electrode lug, a negative electrode lug and a battery body of the battery;
s2: selecting a large-size square lithium battery, developing experimental design, carrying out experiments, preprocessing battery data, and establishing a characteristic test, a constant-current working condition and a dynamic working condition data set of the battery;
s3: in the overview of the high-efficiency heat production calculation method calculated at the present stage, a widely-applied heat production calculation method is selected as an analysis object, and quantitative analysis and comparative research are carried out on the basis of the established electric-thermal coupling model and the collected experimental data set;
s4: each thermal/electric heating submodel in the parametric electric thermal coupling model quantitatively analyzes error sources possibly introduced into the parametric electric thermal coupling model;
s5: researching the thermal interaction between the battery tab and the battery body, and quantitatively analyzing the influence of the heat conduction between the battery tab and the battery body on the temperature distribution of the battery body;
s6: and comprehensively analyzing error sources possibly introduced in the control-oriented electrothermal coupling modeling process to obtain a group of optimal simulation combinations, and verifying the simulation precision and the universality of the combination by experiments.
2. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in S1, for the positive and negative electrode tabs of the battery, in consideration of the material characteristics and the smaller geometric dimensions of the tabs, a concentrated mass model of the positive and negative electrode tabs of the battery is established to describe the thermal behavior of the region; aiming at the battery body, establishing a two-dimensional low-order electrical thermal coupling model to describe the thermal behavior of the region; and establishing a heat transfer model for describing the thermal interaction between the battery body and the anode and cathode lugs.
3. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in the step S2, the designed and implemented experiments comprise a characteristic experiment, a constant current discharge experiment and a dynamic working condition experiment of the battery, wherein the characteristic experiment comprises a static capacity test and a mixed pulse power characteristic test HPPC of the battery at different temperatures, the constant current discharge experiment comprises constant current discharge tests at different multiplying powers, and the dynamic working condition experiment comprises a federal city driving working condition FUDS and a new standard European cycle test working condition NEDC at different temperatures; in addition, the preprocessing of the battery data mainly comprises the steps of removing abnormal data, supplementing missing data and reducing noise of the data, and the established experimental data set comprises current, voltage and temperature data of each measuring point.
4. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in S3, the heat generation calculation method includes three methods: the method based on the equivalent internal resistance can be divided into a voltage difference method and a parameter identification method based on an equivalent circuit model according to the acquisition mode of the equivalent internal resistance.
5. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in the step S4, the parameterization of each thermal/electric thermal submodel in the electrical-thermal coupling model refers to the parameterization of the concentrated mass thermal model of the positive and negative electrode tabs and the parameterization of the two-dimensional low-order electrical-thermal coupling model of the battery body; in the parameterization process of the concentrated mass thermal model, the influence of the working temperature of the battery, the external cooling condition, the current multiplying power and the loading working condition on the model parameters is considered; in the parameterization process of the two-dimensional low-order electrical-thermal coupling model, the influence of the temperature measuring point combination on the parameterization precision of the model is mainly considered.
6. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in S5, the influence of the thermal conduction between the battery tab and the battery body on the temperature distribution of the battery body is quantitatively analyzed by evaluating the prediction accuracy of the electrical-thermal coupling model in consideration of and without consideration of the thermal interaction between the battery tab and the battery body.
7. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 1, wherein the method comprises the following steps: in the S6, the relative root mean square error RRMSE is used as an evaluation index, the prediction precision of the highest temperature and the maximum temperature difference of the battery is mainly considered, all possible error sources in the control-oriented electrothermal coupling simulation process are comprehensively analyzed, a group of optimal simulation combinations are obtained, and then the prediction precision and the universality of the optimal simulation combinations are verified under different working condition scenes.
8. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery as claimed in claim 2, wherein: the heat production item for establishing the concentrated mass models of the positive and negative electrode lugs of the battery only considers ohm heat production; for the two-dimensional low-order electrical-thermal coupling model of the battery body, calculating a heat production term based on a typical Bernardi heat production formula, and considering that the heat production of the battery body comprises reversible heat and irreversible heat; in addition, for the heat transfer behavior of the battery body, a two-dimensional energy conservation equation is used for description, the model reduction of the two-dimensional partial differential equation is realized by utilizing a Chebyshev-Galerkin approximation method, and the two-dimensional partial differential equation is converted into a plurality of ordinary differential equations for solving; for the heat flow exchange between the positive and negative electrode lugs and the battery body, an empirical heat conduction equation is used for simulation, and the heat flow exchange quantity needs to be reasonably distributed to each discrete unit according to the heat flow conduction distance; according to the model order reduction method of the present invention, the battery body can be discretized into a plurality of units.
9. The method for analyzing the electric-thermal coupling modeling error source of the square lithium battery according to claim 4, wherein the method comprises the following steps: in the heat generation calculation method, simulation accuracy is compared, and the heat generation calculation method is indirectly evaluated by the prediction accuracy of a final model by comprehensively considering the heat generation calculation method and other factors influencing battery electric-thermal coupling modeling.
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